"It's exciting because it opens the field up," says Michael Greenberg, a neurobiologist at Harvard Medical School. "Nobody has [found] a gene that controls the process in quite that way before."

The brain is continually trying to strike a balance between too much and too little nerve cell activity. Neurologists believe that when the balance tips, disorders such as autism and schizophrenia may occur. They are not sure why neurons (nerve cells) go berserk. But Greenberg says he and his colleagues located a gene in mice and rats that helps keep neural activity in check—and may one day be manipulated to prevent or reverse neurological problems.

Researchers report in Nature that they discovered a gene called Npas4 churns out a protein that keeps neurons from becoming overexcited when they fire (communicate with one another through connections known as synapses). When scientists blocked the protein, the nerve cells fired or sent out more signals than normal; when they beefed up production, the neurons quieted down.

Gina Turrigiano, a neuroscientist at Brandeis University who studies how brain cells communicate, says Greenberg's study reveals a "pretty intriguing potential pathway" for controlling neuronal activity. But she points out that Npas4 may not be the only gene that does that. Mice without Npas4 can survive, although they are prone to seizures and have a shorter life span than normal mice.

As scientists learn more about how brain cells stay balanced, Greenberg says they will be able to identify people who are genetically at risk for neurological disorders and develop new drugs to prevent and treat them. He notes that some of the other genes that Npas4 affects also have been linked to autism. But he cautions that new therapies from his research are "a long way off." "There's a lot that we don't know," he says. "We're just at the beginning."